Hydraulic transmission fluid containing seal swelling additive and method for reducing fluid leakage



United States Patent 3,389,088 HYDRAULIC TRANSMISSION FLUID CONTAIN- ING SEAL SWELLING ADDITIVE AND METH- 0D FOR REDUCING FLUID LEAKAGE Wayne C. Schar, Middletown, and Donald Borden, Franklin Park, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed May 28, 1963, Ser. No. 283,696 4 Claims. (Cl. 252-73) ABSTRACT OF THE DISCLOSURE An automatic transmission fluid having a mineral lubricating oil base and containing 1 to 5 volume percent of an aliphatic alcohol of from 8 to 13 carbon atoms. The alcohol imparts to the fluid the property of swelling seals in an automatic transmission and thereby prevents leakage.

The present invention relates to an improved hydraulic transmission fluid and particularly concerns an additive for such a fluid that will improve its seal swelling properties without at the same time imparting any detrimental effects thereto. The invention is also directed to an additive concentrate that is intended for incorporation into hydraulic transmission fluids that are in use, where the need for improved seal swelling properties has become manifest.

A very high percentage of automotive vehicles are now equipped with some type of semi-automatic or fully automatic transmission. These transmissions must be provided with a supply of fluid that serves the multiple functions of a power transmitting medium, a hydraulic control fluid, a heat transfer medium, and a satisfactory lubricant. An automatic transmission fluid must be capable of operating over a wide temperature range, it must possess a high degree of oxidation resistance, and it must be free of corrosive action.

While the majority of automatic transmission fluids that are now available commercially do perform satisfactorily, there has been a need to improve their properties with respect to freedom from leakage. It has been estimated that nearly 50% of the automatic transmissions in use on automobiles at the present time are losing significant quantities of automatic transmission fluid, principally because of deterioration of the rubber-type seals or gaskets. As a result of this there have been numerous attempts to develop a composition that can be added to the fluid that is present in an automatic transmission to revitalize the leaking seals or gaskets by swelling and softening the rubber in those seals. An additive for this purpose must not be too potent in its rubber swelling properties because excessive swelling and softening of the transmission seals will cause seal failure. Also, the additive must not lower the viscosity of the automatic transmission fluid nor impair its oxidation stability.

In accordance with the present invention, it has been found that a very effective additive concentrate for reducing fluid loss by the deterioration of the various seals and gaskets associated with the transmission consists of a composition made up of from about 25 to 80 weight percent (approximately 30 to 90 volume percent) of an aliphatic alcohol in the C to C range in a base stock of sufficient viscosity so that the blend will have a viscosity of at least 46.5 SSU at 210 F. The upper practical limit of viscosity for the composition is about 3200 SSU at 210 F. Particularly useful blends of aliphatic alcohol and base stock have viscosities in the range of about 50 to about 200 SSU at 210 F.

The base stock may comprise a high viscosity mineral oil such as an extracted bright stock. More preferably it 3,389,088 Patented June 18, 1968 comprises a lighter mineral lubricating oil with sufficient viscosity index improver to impart the required viscosity to the mixture of base stock and tridecyl alcohol.

The viscosity index improvers that may be employed may include any of the types known to the art, including olefin polymers such as polyisobutylene, carboxylic ester polymers such as the polymethacrylates, e.g. poly dodecyl methacrylate, copolymers of unsaturated dicarboxylic acid esters with other monomers, e.g. a copolymer of mixed C -C alkyl fumarates, maleic anhydride and vinyl acetate, and the like.

It is particularly preferred that the composition of the invention also contain one or more detergent-inhibitors, which will enable the composition to extend the oxidation life of the transmission fluid to which it is added. Such detergent-inhibitors include alkaline earth metal salts of alkyl phenol thioethers having preferably C to C alkyl side chains, e.g. calcium nonyl phenol sulfide, barium tert. octyl phenol sulfide, or the like, the so-called overbased or high alkalinity alkaline earth metal sulfonates derived from hydrocarbon sulfonic acids in the 300 to 800 molecular weight range, and the products obtained by reaction of a phosphosulfurized hydrocarbon with an alkaline earth metal oxide or hydroxide, preferably in the presence of an alkylated phenol or of an alkyl phenol thioether, and also preferably in the presence of carbon dioxide. Phosphosulfurized hydrocarbons are prepared by reacting a suitable hydrocarbon such as a terpene, a heavy petroleum fraction, e.g. a bright stock, or a C to C olefin polymer of a molecular weight in the range 500-200,000 Staudinger, e.g. 1200 mol. wt. polyisobutylene, with from 5 to 30 weight percent of a sulfide of phosphorus, e.g. 15 wt. percent of P 8 for /2 to 15 hours, e.g. 8 hours, at a temperature in the range of to 600 F., e.g. about 450 F. Neutralization of the phosphosulfurized hydrocarbon may be effected in the manner taught in U.S. Patent 2,969,324, for example.

For convenience in blending, commercial V.I. irnprovers are usually available as concentrates containing some 20 to 50 weight percent of active material, and commercially available detergent-inhibitors are normally supplied as concentrates containing in the range of 30 to 70 weight percent of active material.

Particularly preferred for the practice of the present invention are compositions having from about 25 to 60 weight percent of a C to C alcohol, from about 5 to about 10 weight percent of a viscosity index improver, and from about 5 to 15 wt. percent of a detergent-inhibitor, the balance of the composition being a mineral lubricating oil. This additive concentrate is designed for addition to an automatic transmission fluid in such concentrations that from about 1 to 5 volume percent of the alcohol will be supplied to the fluid. The automatic transmission fluids to which the invention is particularly directed are those of the automotive type that meet the viscosity limitations of GM specification Type A, Suffix A, i.e. those having a minimum viscosity when new of 49 SUS at 210 F. (used viscosity 46.5 SUS at 210 F.) and maximum Brookfield viscosities of 4500 cs. at -l0 F. and 64,000 cs. at -40 F.

Especially effective for use in this invention is a mixture of C branched chain alcohols, referred to herein as tridecyl alcohol, prepared by the well-known oxo process in which an olefin, as for example a C olefin such as tetrapropylene, is reacted with carbon monoxide and hydrogen in the presence of a suitable catalyst and the resulting aldehydes are hydrogenated in a separate catalytic step to the corresponding alcohols. Other useful alcohols are decyl alcohol, dodecyl alcohol and octyl alcohol as well as mixed C oxo alcohols. Also, a particularly effective treatment of automatic transmission fluids to im- Example 1 A seal-swelling additive concentrate suitable for use in the present invention was prepared by simply mixing of 50 volume percent of tridecyl alcohol (C oxo alco- 1101), 30 volume percent of a v.1. improver consisting of a concentrate of 80 weight percent of mineral lubricating oil and 20 weight percent of polyisobutylene of 19,000 molecular weight along with 20 volume percent of a detergent-inhibitor concentrate of an additive characterized as a colloidal complex of phosphosulfurized hydrocarbons, barium alkyl phenate and barium carbonate in mineral oil, prepared by reacting a polyisobutylene of about 940 molecular weight with 15 weight percent P 8 mixing the product with nonyl phenol and mineral oil and reacting the mixture with barium hydroxide and carbon dioxide at 250-300 F. for 6 to 10 hours to form a product having a representative weight percent composition as follows:

Percent Phosphosulfurized polyisobutene 27.0 Alkyl phenol (248 average molecular wei ht) 11.7 Barium oxide 10.6 Carbon dioxide 2.5 Mineral oil 48.2

were each subjected to further EBOT testing and to rubher swelling tests in accordance with ASTM D471 for 70 hours at 300 F. using Buna N rubber seals (Acadia 3612). The results obtained are shown in Table 1. It will be seen from the data that the additive concentrate not only improved the rubber swelling properties of the fluid but also extended the oxidation life.

TABLE I Used Fluid Plus Used Fluid Additive Hours to Break Point (EBOTLUA. 24 72 Rubber Swell, Vol. Percent... l 4. 1 +5. 2 SUS Viscosity at 210 F 46. 8 48. 1

Example 3 A Plymouth Torqueflite transmission was filled with 10 quarts of an automatic transmission fluid of Type A, Suffix A quality, consisting of a blend of paraffinic and naphthenic mineral lubricating oils containing a viscosity index improver and a detergent additive and having a viscosity of about 49 SSU at 210 F. After 1 pint of the additive concentrate of Example 1 was also added, the transmission was operated for 40,000 miles without drain in the mileage accumulation dynamometer test described in the aforementioned paper of Deen and Stendahl. At the end of the test the transmission was disassembled and examined thoroughly. The various parts were rated as to cleanliness on the basis of a rating of 10 for a perfectly clean part and 0 for a part containing as much sludge or varnish as it could possibly hold. The inspection results are shown in Table II.

TABLE II.P..ESULTS OF M A D TRANSMISSION TEST [Operating conditions: 40,000 miles, stop and go, no fluid drain, Plymouth Torqucflite tran mission] 3. Miscellaneous:

Brass Thrust Washers Clutch Plates Nylon Speedometer Gear No (liStolora ion or excessive wear N0 pitting or 1 it No signs 01 so mg or wear The additive concentrate comprising the tridecyl alco hol, the viscosity index improver and the detergent-inhibitor had a viscosity of 110 SSU at 210 F, a viscosity at 100 F. of 919 SSU, and a viscosity index of 126.5.

Example 2 A used automatic transmission fluid was prepared by running a fresh sample of a commercial automatic transmission fluid in the Enjay Bench Oxidation Test until incipient failure was indicated, based on previous testing (144 hour point). This test (EBOT) is described in a paper entitled Oxidation Stability, Shear Stability and Rubber Swell Properties of Automatic Transmission Fluids, presented by H. E. Deen and C. M. Stendahl at the SAE 1959 Fuels and Lubricants Meeting held in October 1959 at Chicago, Ill.

To one portion of the used automatic transmission fluid thus obtained, 4.2 volume percent of the additive concentrate of Example 1 was added, representing a 16- ounce treat for 12 quarts. The treated portion of the used automatic transmission fluid and the untreated portion it will be seen that all of the parts had a 10 merit rating for both sludge and varnish, which indicates an exceptionally clean transmission. None of the parts showed more than mild evidence of wear. The clutch plates were also in excellent condition. Of particular importance is the fact that the transmission seals were practically like new, that is they were still soft and pliable.

Example 4 A Chevrolet Powerglide transmission was filled with a commercial transmission fluid to which 4.2 volume percent of the additive concentrate of Example 1 had been added. The transmission was then operated for 80,000 miles, without fiuid drain, in the mileage accumulation dynamometer test as described in Example 3. The transmission Was disassembled at the end of the test and rated in the same manner as in Example 3. The inspection results are given in Table III. The ratings indicate an exceptionally clean transmission for 80,000 miles of driving without fluid drain.

TABLE III.RESULTS OF M A D TRANSMISSION TEST [Operating conditions: 80,000 miles, stop and go, no iluid drain, Chevrolet Powerglide 2. Rubber Seals:

Front Pump Seal (Silicone) Rear Seal (Bun-a Y) Clutch and Servo Seals (Polyacrylie). 3. Miscellaneous:

Soft and Flexible Soft-No Hardening N o Hardening or Cracks Thrust Washers No Excessive Wear or Discoloration Clutch Plates Nylon Gear No Signs of Wear No Pitting or Flaking Example 5 A 16 ounce portion of the additive concentrate of Example 1 was added to the transmission of each of a number of cars having transmission leaks, these leaks amounting in some instances to as much as 1 quart in 500 miles. In each case the leaks Were stopped successfully. The cars included 1956, 1958 and 1959 Oldsm-obiles, 1953, 1957 and 195 8 Chevrolets, a 1956 Plymouth, a 1959 Rambler, and a 1960 Ford.

Example 6 TABLE IV.RESUL'J.S OF EBOT TEST Alcohol used: Hours to break point None 300 Isooctanol 360 n-Decanol 336 Tridecyl alcohol (C oxo) 360 It is to be understood that the examples presented in the foregoing specification are merely illustrative of this invention and are not intended to limit it in any manner; nor is the invention to be limited by any theory regarding its operability. The scope of the invention is to be determined by the appended claims.-

What is claimed is:

1. A method for reducing leakage of fluid in an automatic transmission having rubber-type seals subject to deterioration and containing an automatic transmission fluid having a mineral lubricating oil base which comprises adding to said transmission fluid 1 to 5 volume percent of an aliphatic alcohol of from 8 to 1'3 carbon atoms, whereby said alcohol causes said seals to soften and swell, thereby reducing leakage.

2. A method according to claim 1 wherein said automatic transmission fluid has a minimum viscosity of 46.5 SUS at 210 IF. and maximum iBroolrfield viscosities of 4500 cs, at 10 F. and 64,000 cs. at --40 F., and wherein the alcohol is added admixed with sufiicient lubricating oil viscosity index improving agent to substantially prevent a lowering of viscosity of the automatic transmission fluid by said addition of alcohol.

3. An automatic transmission fluid comprising a major proportion of mineral luricating oil, and from 1 to 5 volume percent of an aliphatic alcohol of from 8 to 13 carbon atoms, said alcohol imparting to the said fluid the property of swelling seals in an automatic transmis sion and thereby preventing leakage.

4. A transmission fluid as defined by claim 3 wherein said aliphatic alcohol is tridecyl alcohol.

References Cited UNITED STATES PATENTS 2,610,948 9/1952 Morway et al. 252-52X 3,039,967 6/1962 Henry et al. 252-- 3,117,929 l/ 1964 McCoy et al. 25273 X LEON D. ROSDOL, Primary Examiner.

JULIUS GREENWALD, ALBERT T. MEYERS,

Examiners.

R. D. LOVERING, Assistant Examiner. 

